This invention pertains to a tubing protector and more particularly to an apparatus for protecting small diameter tubular members secured along the outside of the joints in a pipe string to be used in a borehole.
It is often desirable to pass a small diameter tubing, capillary conduit, wire or the like (hereinafter collectively referred to as "tubular member") into a borehole to provide communication between the surface and the bottom of the borehole. For example, it may be useful to communicate downhole pressure data to the surface by transmitting the fluid pressure via a small diameter capillary tubing. Such a system is illustrated in U.S. Pat. No. 3,895,527.
Capillary tubing systems were initially developed for surface recording of bottom hole pressures. Typically, these systems were used in wells up to ten thousand feed deep and on land rather than offshore, where holes, while not straight, do not have extreme deviations.
Capillary tubing systems have also been used for the transportation of chemicals to wellbore bottoms to treat the fluids and/or formation from which such fluids are being produced. Chemical injection has been used to control corrosion in wells by continuous injection of a chemical inhibitor. The advantages gained by applying the continuous injection procedure in oil and gas wells is well known and many procedures and equipment configurations have been field tested. The two methods most widely used are kill string tubing and the injection of inhibitor packer fluid through a bottom hole valve providing a port between the casing annulus and tubing.
While capillary systems have not been used for the transmission of inhibitors or used in deep, highly deviated holes, they have been successfully used both pneumatically for surface recording of bottom hole pressures and hydraulically for injection of single component, low viscosity liquids in straight holes at relatively shallow depths.
In relatively straight holes, standard types of tubing protectors can be modified for positioning and protecting the tubular member. However, standard protectors are not suitable for use in deep, high angle, high temperature wells.
The foregoing background information is set forth in greater detail in a paper entitled, "Corrosion Protection By Downhole Continuous Inhibitor Transmission Via External Capillary," Paper No. 268 presented at Chicago, Ill. to the National Association of Corrosion Engineers on Mar. 3-7, 1980.
When the above-described tubular communication is used in a borehole, the small diameter tubular member is typically passed along the outside of the pipe string and attached thereto as the tubing or pipe string is introduced into the borehole as illustrated in U.S. Pat. No. 3,757,387. The pipe string is normally comprised of pipe sections which are coupled together with threaded connectors formed integrally on each end of the pipe sections to form a pipe joint. These pipe joints typically are of a greater diameter than the remaining portions of the pipe string. When small diameter tubing is passed along the pipe string, it must necessarily pass over each pipe joint.
As the pipe is introduced into the borehole, the large diameter joints tend to press the small diameter tubing against the wall of the borehole causing wear and damage to the tubular member. Performation or rupture may also result from twisting of an unsecured and unprotected tubular member as the drill string turns, particularly at a pipe joint where the tubular member may be pressed against the borehole wall. Additionally, an unsecured tubular member, as a result of its length and weight, may stretch and thereby deform its interior bore. Such stretching may also cause the tubular member to rupture. Therefore, it is desirable to provide a tubing protector capable of protecting and securing the tubular member at the pipe joints.
In order to provide a fit that will not slip on the pipe and which will hold the tubular member in place, it is necessary to utilize a protector that will fit the dimensions of the pipe joint. There are many types and sizes of pipe joints. Accordingly, tubing protectors in a large variety of sizes are required. The manufacture and cost of this variety of tubing protectors has been a major problem. Therefore, it is desirable to provide a protector capable of being easily and inexpensively manufactured in a wide variety of sizes.
Additionally, protectors which are oval or have outwardly projecting portions tend to hang on the borehole wall. In deviated holes, when the protector hangs, the pipe rotates within the protector thus causing the tubular member to twist and distort. Accordingly, it is desirable to provide a protector having a circular outer surface with no outwardly projecting portions and a smooth transition area from pipe string to protector to minimize hang in the borehole.
The above problems have created the need for a special type of tubing protector for use with small diameter tubular members. The present invention provides a new and improved tubing protector device which will not slip on the pipe, which will prevent wear and damage to a tubular member passing along the outside of a pipe string, which closely fits the dimension of the pipe joint connection, which performs satisfactorily in a highly deviated borehole and which is easily and inexpensively manufactured in a variety of sizes.